The disclosed invention is related to wear detection for belts. More specifically, the disclosed method and apparatus are directed to early warning wear detection for helical offset tooth belts. The disclosed method is highly useful in determining early wear of vehicle timing belts.
Conventional synchronous drive belts have teeth placed at right angles to the belt mid-circumferential line. Such belts are well illustrated in U.S. Pat. Nos. 4,108,011 and 4,690,664. In these known prior art belts, the whole tooth engages with a corresponding pulley cavity at the same time. When such belts wear, the belt begins to oscillate from side to side on the pulleys. To prevent the belt oscillation from pulling the belt off of the drive system, the pulleys of the system are provided with flanges. Wear of such belts is determined by either visual inspection of cracks or breaks, or complete failure of the belt.
U.S. Pat. No. 5,209,705 discloses a synchronous drive belt with at least two transversely adjacent rows of teeth, having centerlines, uniformly spaced apart in the longitudinal direction by a pitch length and extending obliquely to the longitudinal directional. The teeth in the transversely adjacent rows are at oppositely balanced angles and the centerlines of said adjacent teeth are offset from each other by a distance of from 10% to 90% of the pitch length. Such belts are known in shorthand terminology as helical-offset-tooth (HOT) belts. Due to the tooth configuration, the HOT belt is a self tracking belt, that is, there is no normal oscillation of the belt during belt operation. The associated pulleys reflect this aspect of the belt, in that the pulleys are not provided with flanges.
Other types of known self-tracking belts are non-offset teeth belts, wherein the belt has at least two transversely adjacent rows of teeth, the teeth having centerlines extending obliquely to the longitudinal direction. These belts have teeth formed in a chevron pattern. The pulleys associated with chevron toothed belts also do not require flanges, since there is no oscillation of the belt.
The disclosed invention is directed towards the use of a warning system for synchronous belts. The warning system may also be a multiple stage warning system. The disclosed invention may be employed with any synchronous self-tracking belt, such as the HOT belt and chevron tooth belt, and has great applicability for automotive timing belts.
Currently, every vehicle engine has a timing mechanism, either a timing belt or timing chain, for operation of the engine. When the timing mechanism is worn, complete failure of the mechanism results in permanent engine damage, or at best, strands the motorist. There is no automatic detection system or method for determining wear of a timing belt, only physical inspection is possible and is not completely accurate.
U.S. Pat. No. 4,626,230 discloses a device for sensing damage to a toothed belt. However, the sensing device only detects wear of the belt due to tooth breakage, and cannot determine the wear of the belt due to the teeth being worn down during the life of the belt, which also necessitates the replacement of the belt.
Because of the extreme results at failure, one preventative measure is automatic replacement of the belt every 60,000 miles, regardless of the actual wear of the belt. The other conventional method of avoiding catastrophic failure is to use a timing chain, instead of a belt. The timing chain becomes very noisy long before failure occurs alerting the driver to the problem so the chain can be replaced. However, timing chains are heavy and the total drive system is more expensive than a belt drive system.
The present invention will result in more timely assessment of replacement for engine timing belts and less reliance on inaccurate human assessment of belt wear, as well as enable vehicle manufacturers to use the less expensive, lighter weight belt drive systems. The present invention will lead to fewer unnecessary replacements of belts.
The goal of the present invention is an improved wear detection system for use with a synchronous self-tracking belt.
A further aspect of the invention is a two stage warning system for belt wear.
A further aspect of the invention is a multiple stage belt wear detection system.
A benefit of the disclosed invention is a soft failure warning system which prevents catastrophic failure of the synchronous self-tracking drive belt.
The invention is a system employing a helical offset tooth belt and a sensor near at least one side of the belt.
The invention may also employ a sensor mounted on the opposite side of the belt.
The invention may also employ sensors mounted near the belt to provide for a two-stage or multi-stage wear detection system.
One benefit of the disclosed invention is a wear detection system for automotive timing belts.
A further benefit of the invention is a two stage warning system for automotive timing belts.
A further benefit of the invention is a multiple stage wear detection system for automotive timing belts.